#ifndef _CRT_SECURE_NO_WARNINGS
#define _CRT_SECURE_NO_WARNINGS 1
#endif

#include<iostream>
#include<vector>
#include<algorithm>
#include<string>
#include<cmath>
using namespace std;
/*
http://ybt.ssoier.cn:8088/problem_show.php?pid=1241
*/
vector<int>a;

inline double F(double x) {
	double a = 1, b = -15, c = 85, d = -225, e = 274, f = -121;
	return a * x * x * x * x * x + b * x * x * x * x +c * x * x * x +d * x * x +e * x +f;
}

void ac() {
	const double dlt = 1e-7;
	double l = 1.5, r = 2.4;
	while (r - l > dlt) {
		double mid = (r + l) / 2;
		if (F(mid) > dlt)
			l = mid;
		else
			r = mid;
	}
	printf("%.6lf", l);
}

int main() {
	ac();
	return 0;
}